Mga2p processing by hypoxia and unsaturated fatty acids in Saccharomyces cerevisiae:: Impact on LORE-dependent gene expression
Mga2p processing by hypoxia and unsaturated fatty acids in Saccharomyces cerevisiae:: Impact on LORE-dependent gene expression
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DOI：
10.1128/ec.1.3.481-490.2002
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发表时间：
2002-06-01
期刊：
影响因子：
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通讯作者：
Goldberg, MA
中科院分区：
文献类型：
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作者：
Jiang, YD;Vasconcelles, MJ;Goldberg, MA
在酿酒酵母中，OLE 1编码A9脂肪酸去饱和酶，该酶在维持细胞膜中饱和脂肪酸与单不饱和脂肪酸的正确比例方面起关键作用。以前的研究已经证明，（i）OLE 1的表达被不饱和脂肪酸（UFA）抑制，并由低氧张力诱导，（ii）这种调节的一个组成部分是通过OLE 1启动子中相同的低氧反应元件（LORE）介导的，（iii）Mga 2 p参与OLE 1的LORE依赖性缺氧诱导。我们现在报告，LORE-CYC 1基础启动子-lacZ融合报告基因检测表明，UFA通过LORE以剂量依赖性方式抑制缺氧条件下的报告基因表达。电泳迁移率变动分析表明，UFAs抑制缺氧诱导的复合物与LORE的形成。用编码Mga 2 p截短形式的构建体进行的研究支持以下假设：缺氧和乌法信号均影响Mga 2 p的加工，并且乌法对OLE 1缺氧诱导的抑制是通过Mga 2 p介导的。蛋白质印迹分析的数据提供了证据，表明在常氧条件下，Mga 2 p加工产生大约等摩尔水平的膜结合形式和加工形式，并且不受UFA的影响。然而，OLE 1的低血糖诱导与蛋白质加工的增加有关，导致可溶性活性形式增加约5倍，这被细胞暴露于不饱和脂肪酸所抵消。这项研究的数据表明，Mga 2 p-LORE相互作用在常氧和缺氧条件下的OLE 1表达中起着重要作用。
In Saccharomyces cerevisiae, OLE1 encodes a A9 fatty acid desaturase, an enzyme that plays a critical role in maintaining the correct ratio of saturated to monounsaturated fatty acids in the cell membrane. Previous studies have demonstrated that (i) OLE1 expression is repressed by unsaturated fatty acids (UFAs) and induced by low oxygen tension, (ii) a component of this regulation is mediated through the same low oxygen response element (LORE) in the OLE1 promoter, and (iii) Mga2p is involved in LORE-dependent hypoxic induction of OLE1. We now report that LORE-CYC1 basal promoter-lacZ fusion reporter assays demonstrate that UFAs repress the reporter expression under hypoxic conditions in a dose-dependent manner via LORE. Electrophoretic mobility shift assays show that UFAs repress the hypoxia-induced complex formation with LORE. Studies with a construct encoding a truncated form of Mga2p support the hypothesis that both hypoxia and UFA signals affect the processing of Mga2p and the UFA repression of OLE1 hypoxic induction is mediated through Mga2p. Data from Western blot assays provide evidence that under normoxic conditions, Mga2p processing produces approximately equimolar levels of the membrane-bound and processed forms and is unaffected by UFAs. Hypoxic induction of OLE1, however, is associated with increased processing of the protein, resulting in an approximately fivefold increase in the soluble active form that is counteracted by exposure of the cells to unsaturated fatty acids. Data from this study suggest that the Mga2p-LORE interaction plays an important role in OLE1 expression under both normoxic and hypoxic conditions.